You might be better served asking in the PC thread for more opinions.
I'm playing on a ~$600 HP I got at Staples...runs the game on Medium reasonably well, but I've been playing on low more lately just so I can play longer per sitting. (2 hours on Medium made my comp really start to grind...)
Luckily, Skyrim on low still looks better than most games.
One tip I have is to check on http://www.systemrequirementslab.com/cyri/intro.aspx too.